The present invention relates to processes for recovery of ethane, propane and NGL from natural gas whereby the expander shaft compressor is located in a new locations permitting the reflux generation requirement for the cryogenic absorber and/or gas processing distillation columns.
Current prior art processes for recovery of natural gas liquids comprise:                A large sales gas export compressor that unnecessarily increases utilities, the large size needed to compensate for a high pressure drop across a turbo expander that provides some process refrigeration and dictating a low cryogenic absorber pressure.        A relatively high capacity cryogenic pump to pump a bottoms liquid stream from a cryogenic absorber.        Expander feed gas being at least partly condensed and used as a reflux to a demethanizer, causing loss of propane from a bottoms liquid product.        Process configuration and operating conditions that might result in a lower ethane plus or propane plus recovery (less than 99%). U.S. Pat. No. 6,581,410 B1.        Process configuration and operating conditions whereby maximum heat integration between cold and hot streams are not always optimally effected. This results in a lower outlet temperatures of cold streams and accordingly a lower overall UA.        In propane recovery, relatively large energy consumption in a de-ethanizer bottom reboiler due to operation at pressures higher than a cryogenic absorber.        In propane recovery, a de-ethanizer must be designed with a relatively large diameter.        In propane recovery mode, extra equipment must be installed to provide chilling of feed gas through heat exchange with de-ethanizer side draw.        In ethane recovery, additional multi-flash vessels and LNG multi-stream, platefin heat exchangers are needed to generate multiple reflux streams for an absorber de-methanizer.        Excess carbon dioxide tends to accumulate an NGL product        In propane recovery, additional compressors are needed to recycle de-ethanizer overhead gases to a cryogenic absorber, which operates at a pressure above the de-ethanizer. PCT/US01/20633, WO 02/14763, US 2002/0166336 A1.        In propane recovery, ethane can build up in a gas loop between a de-ethanizer and a cryogenic absorber that makes operation unstable.        In a propane recovery, lean gas and de-ethanizer OVHD gases are recycled back to the cryogenic absorber. US 2004/0148964 A1, WO 2004/057253 A2.        
U.S. Pat. Nos. 6,578,379, 6,278,035, 6,311,516, 6,354,105, 6,453,698, and 6,244,070 generally describe a state of the art using multiple pieces of expensive equipment and/or external refrigeration systems to accomplish high recovery of ethane from NGL. Older references, such as U.S. Pat. Nos. 4,851,020, 4,867,499, and 5,992,175, show ethane recovery systems with somewhat fewer pieces of equipment and less reliance on external refrigeration. The systems in these older references have been found to be incapable of obtaining presently commercially required recovery of ethane from NGL feeds.
Fractionation of the natural gas feed requires that a product stream contain a minimum specified amount of carbon dioxide. Obtaining a low level of carbon dioxide in the product stream has in the past typically required two or more separated fractionation columns processing the natural gas feed.
There is a need for a process that minimizes or eliminates the above problems.